To preheat means to heat an oven or other cooking appliance to the right temperature before you put food inside. When a recipe tells you to preheat the oven to 350 degrees, you turn it on and wait until it reaches that temperature, then slide in your cookies or casserole.

Preheating matters because ovens take time to warm up, usually 10 to 15 minutes. If you put a cake in a cold oven, it won't bake properly: the outside might cook too fast while the inside stays gooey, or the texture might turn out dense and heavy instead of light and fluffy. Many baked goods need that consistent, steady heat from the start to rise correctly and develop the right texture.

The word combines pre (meaning before) and heat. You're heating before the actual cooking begins. While preheating is most common with ovens, you might also preheat a waffle iron, a panini press, or even a skillet before cooking. Getting the temperature right from the beginning helps ensure your food turns out the way it's supposed to.